The renin-angiotensin-aldosterone system (“RAAS”) is one of the hormonal mechanisms involved in regulating pressure/volume homeostasis and also in the development of hypertension, a condition that can progress to more serious cardiovascular diseases such as congestive heart failure. Activation of RAAS begins with secretion of the enzyme renin from juxtaglomerular cells in the kidney.
Renin, a member of the aspartyl protease family, passes from the kidneys into the blood where it cleaves angiotensinogen to generate the decapeptide angiotensin I. Angiotensin I is then cleaved in the lungs, the kidneys and other organs by the angiotensin-converting enzyme (ACE) to form the octapeptide angiotensin II. Angiotensin II, which is known to work at least on two receptor subtypes (AT1 and AT2), increases blood pressure both directly by arterial vasoconstriction and indirectly by liberating from the adrenal glands the sodium-ion-retaining hormone aldosterone. Angiotensin II also produces other physiological effects such as promoting sodium and fluid retention, inhibiting renin secretion, increasing sympathetic nervous system activity, stimulating vasopressin secretion, causing a positive cardiac inotropic effect and modulating other hormonal systems.
Modulation of the RAAS represents a major advance in the treatment of cardiovascular diseases. In particular, the rationale to develop renin inhibitors lies in its specificity (Kleinert H. D., Cardiovasc. Drugs, 1995, 9, 645). The only substrate known for renin is angiotensinogen, which can only be processed (under physiological conditions) by renin. Inhibitors of the enzymatic activity of renin are therefore expected to bring about a reduction in the formation of angiotensin I and angiotensin II.
In view of the foregoing, renin is an especially attractive target for the discovery of new therapeutics for cardiovascular disease, hypertension, congestive heart failure, myocardial infarction, renal protection, inflammation, neurological diseases, cancer, and other diseases. Accordingly, there is a need to find new renin inhibitors for use as therapeutic agents to treat human diseases. In particular, there is a continued need for metabolically stable, orally bioavailable renin inhibitors that can be prepared on a large scale.
Modeling of the active site of renin has now revealed that certain classes of known compounds, including those described in US 2005/072765 A1 US 2006/014764 A1, WO 2005/118555 and WO 2006/020017, may also possess renin activity. Those compounds were previously reported to be DPP-IV inhibitors, but they have now proven to be useful leads in the search for renin inhibitors.